Update CONTRIBUTING.md

CONTRIBUTING.md

@@ -22,6 +22,22 @@ If you encounter a bug or have any suggestion for improving this project, you ca
 
 For more information on the different ways in which you can contribute to RudderStack, you can chat with us on our [**Slack**](https://rudderstack.com/join-rudderstack-slack-community/) channel.
 
+## Adding your own integrations
+
+One way you can contribute to this project is by adding integrations of your choice for sending the data through their respective web (JavaScript) SDKs.
+
+### How to build the SDK
+
+- Look for run scripts in the `package.json` file for getting the browser minified and non-minified builds. The builds are updated in the `dist` folder of the directory. Among the others, some of the important ones are:
+
+  - `npm run buildProdBrowser`: This outputs **rudder-analytics.min.js**.
+  - `npm run buildProdBrowserBrotli`: This outputs two files - **rudder-analytics.min.br.js** (the original minified file, same as above) and **rudder-analytics.min.br.js.br** (the Brotli-compressed file).
+  - `npm run buildProdBrowserGzip`: This outputs two files, **rudder-analytics.min.gzip.js** (the original minified file, same as above) and **rudder-analytics.min.gzip.js.gz** (the gzipped compressed file).
+
+> We use **rollup** to build our SDKs. The configuration for it is present in `rollup.config.js` in the repo directory.
+
+- For adding or removing integrations, modify the imports in `index.js` under the `integrations` folder.
+
 ## Committing
 
 We prefer squash or rebase commits so that all changes from a branch are committed to master as a single commit. All pull requests are squashed when merged, but rebasing prior to merge gives you better control over the commit message.